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WING TUBE CRACK

Hello all:
I have been flying a 42% DALTON for almost a year, not too many flights though.
This week end I noticed a crack in the main wing tube. Fortunately I saw it on time, and the airplane has never hard-landed, not crashed, only snaps on IMAC routines, and the tube properly handled.

I have been asking about it and what I have heard is really scary as the consensus is "probably a bad batch tube" !!
Interesting uh?

I also noticed that this tube has a very thin wall too. This is the original tube shipped when I bought the kit from Dalton Aviation.
The questions are:
1. Are there thicker tubes available ?
2. Dalton: Why not using a bigger diameter tube ? The moment of inertia should be higher for this size of airplanes. Some smaller airplanes have bigger diameter tubes!!!
3. What about aluminum tubes ? I heard that they bend in regular flying, which proves that the stress is gigantic. Is it true they bend?

RE: WING TUBE CRACK

There are several sources for carbon tubes. Try TroyBuilt Models for the exact size you need. Also I think DA sells the PBG line from Aussieland, which have proven excellent over the years. You might also get the right size from Extreme Flight but call them first for the exact size you need. Measure the existing tube with a micrometer or caliper to get the right fit.

Aluminum will definitely bend, even the aircraft grades such as 6061 and 7075. But they won't necessarily break. I don't care for a wing joiner bending so I stick with carbon

RE: WING TUBE CRACK

The tube having a crack is interesting. First off I assume the crack is longitudinal. Meaning running some length of the tube?
Obviously if the crack were lateral, i.e. across the carbon fiber grain, not only would it be surprising but a critical situation particularly if it were oriented at the bottom of your last flight.

So assuming it is running longidtudinal, the question is how did it happen. I am willing to bet it is actually a shear induced fracture. It could be a manufacture defect (temp changes often reveal them)but if it happened in flight it probably appeared as a result of shear. Meaning the crack occurs on the front or back of the tube as the result of tensile load in the extreme top fiber and compressive loading in the bottom fiber, or vice versa if you do a lot of negative G maneuvers. So then it would be interesting to know of the tube has any cross grain fiber layup, i.e in the lateral direciton or even on the 45 would help avoid shear failure. This is where aluminum has an advantage because as a structural material it has good properties all directions.

RE: WING TUBE CRACK

ORIGINAL: sensei

Is the crack at one or both ends of the tube longitudinally? If so there is a reason and an easy fix as well...

Bob

You would never catch me attempting to repair a CF wing tube. 1.5" CF and aluminum wing tubes are very easy to find. Not too long ago I took a couple to the recycling center just because I got tired of looking at them.

RE: WING TUBE CRACK

ORIGINAL: speedracerntrixie

ORIGINAL: sensei

Is the crack at one or both ends of the tube longitudinally? If so there is a reason and an easy fix as well...

Bob

You would never catch me attempting to repair a CF wing tube. 1.5'' CF and aluminum wing tubes are very easy to find. Not too long ago I took a couple to the recycling center just because I got tired of looking at them.

That is because you are most likely ignorant on the subject of composites and do not understand what your looking at in the first place from your statement, so the very best thing for you to do is to throw them away...

RE: WING TUBE CRACK

ORIGINAL: sensei

ORIGINAL: speedracerntrixie

ORIGINAL: sensei

Is the crack at one or both ends of the tube longitudinally? If so there is a reason and an easy fix as well...

Bob

You would never catch me attempting to repair a CF wing tube. 1.5'' CF and aluminum wing tubes are very easy to find. Not too long ago I took a couple to the recycling center just because I got tired of looking at them.

That is because you are most likely ignorant on the subject of composites and do not understand what your looking at in the first place from your statement, so the very best thing for you to do is to throw them away...

Bob

LOL That's funny. I suppose I imagine going to work every day as a composites tech manufacturing composite components for military aircraft. What the heck, I have an open mind. How about you describe the repair process to me.

RE: WING TUBE CRACK

As I stated in my first post, if the cracks are on the ends of the tube longitudinally there is a cause the cracks are starting in the first place and a fix to prevent them from starting in the future. Like I said, your statement of throwing those tubes away tells me you don't know much or you would not have a stock pile of carbon tubes to pitch would you! LOL. You may very well work as a composite tech someplace performing lay-ups or trimming parts to a process spec. somebody like me generates for you to do your job.

RE: WING TUBE CRACK

My post may not have been clear enough but the tubes I took to the recycling center were aluminum. It was in reference that 1.5" 6061 wing tubes are just about everywhere. Don't know how you could have assumed they were CF as that material has no recycle value that I am aware of.

The other assumtion you make is that the cracks are at the end of the tube and could be longitudinally orinted. Not likeley as there are no flight loads that would create that condition. The stress riser is is where the wings and fuse meet, this is where the fracture is going to happen due to flight loads. There is no way a hobbiest can repair that. Even if he could, the materials to do so would come close to the cost of a new tube. So then the question becomes on of why?

Yet another assumption is that demeaning my role at work.Yes I do lay-ups of all sorts including wet lay-ups pre-preg, fibeglass, Astro quartz using female molds, caul plates, compression molds ect but I also work with structural engineers to come up with processes to repair flight damage on 19' roto domes.

RE: WING TUBE CRACK

The reason I am assuming we are talking about carbon tubes is because this thread is about his thin carbon tube cracking.

The stress riser is in fact right at the fuse sides so the best way to minimize the amount of rise is to place a small radii around the root rib wing socket and do the same on the fuse wing sockets as I have demonstrated on many build threads over the years. this radii also keeps the tube from wearing a line in the tube at the highest loaded area.

Everybody knows the load diminishes span wise on the wing/tube, that certainly no front page news however thin carbon wing tubes can and are easily damaged on the ends by simply squeezing or lightly bumping the ends of the tube, these small fractures can run span wise and turn catastrophic, you can easily keep span wise runners from migrating down the tube by just cutting a .250" thick plywood donut for each end of the tube, and installing them about .125" from the ends of the tube with thin CA.

Note: The reason I believe the cracks are on the the ends of the tube is as follows: He never stated he lost the airplane and if he had horizontal cracks around the stress riser areas a thin carbon tube on a 42% aerobatic bird the tube would have gone catastrophic for sure.

RE: WING TUBE CRACK

I will agree that the OP has not stated where the cracks are, I will dis-agree that cracks on the stress riser has to end is catastrophic failure. I have had 2 wing failures in 40% airplanes that did not end up in a crash. The first was my Colombo Extra, the wing tube slid off center and dis-engaged the false rib at mid span. At the end of the flying session I noticed that the wing socket was trying to push out of the bottom of the wing. The second one was an Aeroworks 42% Extra 260. The spars seperated so badly that I could move the wing tip 2 " up and down. I agree that luck would play a huge part in surviving a tube structure at the root but as long as the root rib and fuse side was holding the tube in it's circular shape then it could survive. Having the OP post a couple pics of the failure would clear alot of this up.